Reduced slippage balloon catheter and method of using same

ABSTRACT

A balloon catheter having a balloon with a reduced slippage lubricious coating, and a method of performing a medical procedure such as a balloon dilatation procedure in a patient&#39;s blood vessel. The second coating (i.e., the balloon coating) is lubricious to facilitate movement of the catheter in the patient&#39;s body lumen, yet has sufficiently low lubricity such that the slippage of the inflated balloon from a desired site within the blood vessel is reduced compared to a balloon coated with the first lubricious coating.

BACKGROUND OF THE INVENTION

This application is a divisional of U.S. patent application Ser. No.10/288,783 filed Nov. 6, 2002 now U.S. Pat. No. 7,025,752.

This invention generally relates to catheters, and particularlyprotective sheaths for intravascular catheters for such as ballooncatheters used in percutaneous transluminal coronary angioplasty (PTCA)or for the delivery of stents.

In percutaneous transluminal coronary angioplasty (PTCA) procedures aguiding catheter is advanced in the patient's vasculature until thedistal tip of the guiding catheter is seated in the ostium of a desiredcoronary artery. A guidewire is first advanced out of the distal end ofthe guiding catheter into the patient's coronary artery until the distalend of the guidewire crosses a lesion to be dilated. A dilatationcatheter, having an inflatable balloon on the distal portion thereof, isadvanced into the patient's coronary anatomy over the previouslyintroduced guidewire until the balloon of the dilatation catheter isproperly positioned across the lesion. Once properly positioned, thedilatation balloon is inflated with inflation fluid one or more times toa predetermined size at relatively high pressures so that the lesion iscompressed against the arterial wall and the wall expanded to open upthe vascular passageway. Generally, the inflated diameter of the balloonis approximately the same diameter as the native diameter of the bodylumen being dilated so as to complete the dilatation but not overexpandthe artery wall. After the balloon is finally deflated, blood flowresumes through the dilated artery and the dilatation catheter and theguidewire can be removed therefrom.

In such angioplasty procedures, there may be restenosis of the artery,i.e. reformation of the arterial blockage, which necessitates eitheranother angioplasty procedure, or some other method of repairing orstrengthening the dilated area. To reduce the restenosis rate ofangioplasty alone and to strengthen the dilated area, physicians nownormally implant an intravascular prosthesis, generally called a stent,inside the artery at the site of the lesion. Stents may also be used torepair vessels having an intimal flap or dissection or to generallystrengthen a weakened section of a vessel or to maintain its patency. Atubular cover formed of synthetic or natural material may be present onan outer or inner surface of the stent. Stents are usually delivered toa desired location within a coronary artery in a contracted condition ona balloon of a catheter which is similar in many respects to a balloonangioplasty catheter, and expanded within the patient's artery to alarger diameter by expansion of the balloon. The balloon is deflated toremove the catheter and the stent left in place within the artery at thesite of the dilated lesion. See for example, U.S. Pat. No. 5,507,768(Lau et al.) and U.S. Pat. No. 5,458,615 (Klemm et al.), which areincorporated herein by reference.

An essential step in effectively performing a PTCA procedure is properlypositioning the balloon catheter at a desired location within thecoronary artery. To facilitate advancement of the catheter within thetortuous vasculature, conventional balloon catheters for angioplasty andstent delivery frequently have a lubricious coating on at least aportion of an outer surface of the catheter. However, one difficulty hasbeen the tendency of the balloon having a lubricious coating thereon toslip out of position during inflation ofthe balloon. Accordingly, itwould be a significant advance to provide a catheter balloon havingimproved balloon retention, and without inhibiting movement of thecatheter within the vasculature.

SUMMARY OF THE INVENTION

This invention is directed to a balloon catheter having a balloon with areduced slippage lubricious coating, and a method of performing amedical procedure such as a balloon dilatation procedure in a patient'sblood vessel.

The balloon catheter of the invention generally includes an elongatedshaft having a proximal end, a distal end, an inflation lumen, and afirst lubricious coating with a first amount per unit area of lubriciousmaterial on at least a portion of the shaft, and a balloon on a distalshaft section having an interior in fluid communication with theinflation lumen, and a second lubricious coating on at least a portionofthe balloon, the second lubricious coating having a second amount perunit area of lubricious material which is less than the first amount perunit area of lubricious material. In a presently preferred embodiment,the shaft includes a distal tip section, which in one embodiment isformed of a separate distal tip member, having at least a portion distalto the balloon and coated with the second lubricious coating. In oneembodiment, the shaft comprises an outer tubular member defining theinflation lumen, and an inner tubular member defining a guidewirereceiving lumen extending in at least a distal portion of the outertubular member, and the first lubricious coating is on an outer surfaceof a proximal and a distal section of the outer tubular member definingan outer surface of the catheter. The second lubricious coating on theballoon preferably extends along the entire length of an outer surfaceof the balloon, although in alternative embodiments, the secondlubricious coating may be on less than the entire outer surface of theballoon, and for example may be on intermittent portions of the balloonouter surface.

In one embodiment, the lubricious material of the first and secondcoating is a hydrophilic material, and in a presently preferredembodiment, is a polyethylene oxide based lubricious coating. However, avariety of suitable lubricious materials can be used includinghydrophobic materials. In a presently preferred embodiment, thelubricious material of the first and second coatings is the samelubricious material, but, in accordance with the invention, is appliedso that the balloon is coated with a smaller amount per unit area of thelubricious material, and thus a less lubricious coating, than at leastthe part of the shaft proximal thereto. The second coating (i.e., theballoon coating) is lubricious to facilitate movement of the catheter inthe patient's body lumen, yet has sufficiently low lubricity such thatthe slippage of the inflated balloon from a desired site within theblood vessel is reduced compared to a balloon coated with the firstlubricious coating. The coated balloon inflates into contact with, andremains at least partially in contact with a stenosed section of theblood vessel. Thus, the balloon catheter provides for improveddilatation of the desired region of the blood vessel by reducing thetendency of the lubriciously coated balloon to slip proximally ordistally from the stenosed section of the blood vessel. The firstlubricious coating on the balloon is relatively highly lubricious andthus facilitates movement of the catheter in the body lumen.

The second coating has a relatively small amount of lubricious material,to thereby provide a balloon surface which is more lubricious than abare (non-coated) balloon, yet which has an insubstantial amount ofslippage when inflated into contact with the blood vessel. Preferably,the second amount of lubricious material per unit area is not more thanabout 2.5% to about 3% of the first amount per unit area, and is mostpreferably about 1% to about 2.5% of the first amount per unit area. Thecoatings can be applied using a variety of suitable methods includingwiping, spraying, and dipping solutions of the lubricious material ontothe outer surface of at least a portion of the shaft and at least aportion of the balloon. The solutions on the catheter are typicallycured to produce the lubricious coatings on the catheter. The curedlubricious coatings typically consist of the lubricious material and amatrix material. In a presently preferred embodiment, the first andsecond solutions which are applied to the catheter to form the first andsecond coatings, respectively, have an amount of lubricious material inthe same proportion as in the cured coatings (i.e., the concentration oflubricious material in the second solution is not more than about 2.5%to about 3% of the concentration of lubricious material in the firstsolution). In a presently preferred embodiment, the second solution isprepared by diluting the first solution with additional solvent, withthe absolute amount of lubricious material being about the same in thetwo solutions. As a result, after removal of the solvents during curingof the coatings on the balloon and shaft, the concentration oflubricious material (grams of lubricious material per gram of curedcoating) of the second cured coating on the balloon is the about thesame as the concentration of lubricious material of the first curedcoating on the shaft. However, in a presently, preferred embodiment,approximately the same amount of solution is applied to the shaft as tothe balloon, so that the resulting cured coatings on the shaft and theballoon have an amount (mass) of lubricious material per unit area(gm/in²) in the same proportion as the amount of lubricious material inthe two solutions (i.e., the solution of lubricious material applied tothe balloon has a concentration of lubricious material which is not morethan about 2.5% to about 3% of the concentration of lubricious materialin the solution of lubricious material applied to the shaft, and theresulting mass of lubricious material per unit area in the cured secondlubricious coating on the balloon is not more than about 2.5% to about3% of the mass of lubricious material per unit area in the cured firstlubricious coating on the shaft. However, it should be understood thatthere are a variety of ways of forming the coatings on the shaft andballoon with the desired relative amounts of lubricious material,including applying different amounts of lubricious solution, andapplying lubricious solutions which do not have an amount of lubriciousmaterial in the same proportion as the amount of lubricious material inthe resulting cured coatings on the shaft and the balloon.

The balloon coated with the second lubricious coating has a slip anglewhich is less than a slip angle of a bare (non-coated) balloon andgreater than a slip angle of a balloon coated with the first lubriciouscoating. The slip angle is the critical angle at which the coatedworkpiece will slip out of position. A less lubricious surface has ahigher slip angle than a more lubricious surface. A fixture formeasuring the slip angle generally comprises apolymeric tube, andspecifically a polyvinyl alcohol and dimethyl sulfoxide tube, whichsimulates a blood vessel, and a pusher with a weight which is on anouter surface of the tube and which can be oriented at different anglesrelative to the polymeric tube. The balloon is placed in the tube, withthe angle at which the pusher contacts the tube simulating the angle ofa lesion in a blood vessel, and the angle of the pusher is increaseduntil the balloon slips longitudinally out of position during inflationof the balloon in the tube. Thus, the pusher squeezing on the ballooncauses the balloon to slip longitudinally, and the higher the angle atwhich this slipping first occurs, the less likely the balloon is to slipout of position during inflation of the balloon in a patient's bloodvessel (i.e., the relatively less lubricious the balloon outer surface).In a presently preferred embodiment, two measurements are made, namely,one with the pusher aligned at the balloon distal marker at the distalend of the balloon central working length, and another with the pusheraligned 1 mm proximal to the distal marker. Using this procedure theslip angle can be measured for various coatings to compare the effect ofthe relative lubricity of the various coatings on balloon slippage. Theslip angle of the balloon coated with the second lubricious coating(i.e., the minimum angle of the pusher at which the balloon begins toslip in the polymeric tube) is about 4 to about 10 degrees, preferablyabout 8 to about 10 degrees, and the slip angle of a bare balloon isabout 10 to about 15 degrees, preferably about 12 to about 15 degrees,and the slip angle of a balloon coated with the first lubricious coatingis about 1 to about 7 degrees, preferably about 2 to about 6 degrees. Itshould be noted that at a relatively high angle of about 20 degrees thepusher begins to pinch the balloon and prevent the balloon from slippinglongitudinally in the polymeric tube, so that a slip angle above 20degrees cannot be measured with the slip angle fixture described above.

In a method of performing a medical procedure, a balloon catheter isadvanced within a patient's blood vessel to a desired position at astenosed section, the balloon catheter having a first lubricious coatingwith a first amount per unit area of lubricious material on at least aportion of the shaft and a second lubricious coating with a secondsmaller amount per unit area of lubricious material on at a leastportion of the balloon, and the balloon is inflated so that the balloonworking length contacts and dilates the stenosed section of the bloodvessel. The coated surface of the balloon inflates into direct contactwith the blood vessel wall/lesion, and the second coating limits orprevents the balloon from slipping longitudinally out of position.Preferably, the balloon catheter of the invention has a balloon which isat least about 40% less likely to slip out of position in a patient'sbody lumen during dilatation of a lesion than a balloon catheter havinga balloon with the same lubricious coating as the shaft. In oneembodiment, due to the limited amount of slippage of the balloon, asubstantial portion of the inflated balloon working length remains incontact with the stenosed section of the blood vessel during thedilation. After the dilation, the balloon is deflated, and the catheteris repositioned or withdrawn from the blood vessel. The lubriciouscoatings on the catheter facilitate repositioning or withdrawing thedeflated balloon catheter from the blood vessel.

The balloon catheter can be used for a variety of procedures includingcoronary or peripheral dilatation, drug delivery, intravascularprosthesis delivery and the like. The balloon catheter can have avariety of convention configurations including an over-the-wire typedesign, or a rapid exchange type design. Rapid exchange cathetersgenerally comprise a distal guidewire port in a distal end of thecatheter, a proximal guidewire port in a distal shaft section distal ofthe proximal end of the shaft and typically spaced a substantialdistance from the proximal end of the catheter, and a short guidewirelumen extending between the proximal and distal guidewire ports in thedistal section of the catheter.

The balloon catheter of the invention provides for improved dilatationof a patient's blood vessel, due to the first and second lubriciouscoatings on the shaft and balloon, respectively. The coated balloonsurface has a sufficiently low lubricity to minimize the slippage of theinflated balloon out of position at the lesion during the dilatation,yet sufficiently high lubricity to facilitate movement of the catheterwithin the blood vessel. These and other advantages of the inventionwill become more apparent from the following detailed description of theinvention and the accompanying exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view, partially in section, of a ballooncatheter embodying features of the invention, in a patient's body lumen.

FIGS. 2 and 3 are transverse cross sectional views of the ballooncatheter shown in FIG. 1, taken along lines 2-2 and 3-3, respectively.

FIG. 4 is an enlarged, partially in section, view of the distal end ofthe balloon catheter shown in FIG. 1, with the balloon inflated duringdilatation of the body lumen.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an over-the-wire type balloon catheter 10 embodyingfeatures of the invention. Catheter 10 generally comprises an elongatedcatheter shaft 12 having an outer tubular member 14 and an inner tubularmember 16. Inner tubular member 16 defines a guidewire lumen 18configured to slidingly receive a guidewire 20, and the coaxialrelationship between outer tubular member 14 and inner tubular member 16defines annular inflation lumen 22, as best shown in FIG. 2 illustratinga transverse cross section view of the distal end of the catheter shownin FIG. 1, taken along line 2-2. An inflatable balloon 24 disposed on adistal section of catheter shaft 12 has an elongated cylindricalexpandable working section, a proximal skirt section 25 sealinglysecured to the distal end of outer tubular member 14 and a distal skirtsection 26 sealingly secured to the distal end of inner tubular member16, so that its interior is in fluid communication with inflation lumen22. A distal tip 27 defining the distal end of the guidewire lumen 18 islocated distal to the balloon 24. In the embodiment of FIG. 1, thedistal tip 27 is a separate member butt joined to the distal end of theinner tubular member 16, with the buttjoint located at the distal end ofthe balloon distal skirt section 26. However, in an alternativeembodiment (not shown), the distal tip 27 and inner tubular member 16are an integral, one-piece unit, so that the distal tip 27 is defined bythe exposed outer surface of the distal end of the inner tubular member16 distal to the distal end of the balloon 24. A variety of suitabledistal tip configurations can be used as are conventionally known,including a distal tip having a proximal end surrounded by and bonded toanother component of the catheter. An adapter 28 at the proximal end ofcatheter shaft 12 is configured to provide access to guidewire lumen 18,and to direct inflation fluid through arm 29 into inflation lumen 22.FIG. 1 illustrates the balloon 24 in a low profile tubular configurationprior to complete inflation. The distal end of catheter 10 may beadvanced to a desired region of the patient's blood vessel 30 in aconventional manner, and balloon 24 inflated to expand the balloon 24into contact with the lesion to dilate the stenosed section 31 of theblood vessel, and the balloon deflated and the catheter repositioned inthe blood vessel or withdrawn therefrom. FIG. 3 illustrates a transversecross section view of the distal end of the-catheter shown in FIG. 1,taken along line 3-3.

The outer surface of the outer tubular member 14 has a first lubriciouscoating 40, and the outer surface of the balloon 24 has a secondlubricious coating 41. In the embodiment of FIG. 1, the first lubriciouscoating 40 extends the entire length of the exposed outer surface of theouter tubular member 14 defining an outer surface of the catheter, andthe second lubricious coating 41 extends the entire length of theballoon 24 and over the exposed outer surface of the distal tip 27.Thus, the portion of the outer tubular member 14 covered by and bondedto the proximal skirt section 25 of the balloon is not coated with thelubricious coating 40. The thickness of the coatings 40, 41 areexaggerated in the figures for ease of representation. In the embodimentof FIG. 1, the thicknesses of the cured coating 40 on the outer tubularmember 14 is thicker than the thickness of the cured coating 41 on theballoon 24.

The second lubricious 41 coating has an amount per unit area oflubricious material which is less than the amount per unit area oflubricious material in the first lubricious coating 40, so that thefirst lubricious coating 40 on the outer tubular member 14 is morehighly lubricious than the second lubricious coating 41 on the balloon24. In a presently preferred embodiment, the first coating 40 is appliedby applying a first solution of the lubricious material on the exposedouter surface of the outer tubular member 14 after the catheter has beenassembled (i.e., the balloon secured to the inner and outer tubularmembers). Similarly, the second coating 41 is provided on the balloon byapplying a second solution the lubricious material on the outer surfaceof the balloon 24 and the tip 27. Preferably, the concentration oflubricious material in the second solution is not more than about 2.5%to about 3% of the concentration in the first solution. In a presentlypreferred embodiment, the concentration of the first solution is about1.0 to about 1.3 wt. % lubricious material, and the concentration of thesecond solution is about 0.01 to about 0.03 wt. % lubricious material.The solutions are cured, as for example by drying and/or ultraviolet(UV) curing, to form the coatings 40, 41 on the catheter. In oneembodiment, the lubricious solutions comprise polyethylene oxide andtrimethoylol propane triacrylate in benzophenone, hydrophenyl ketone and1-hydroxycyclohexyl phenyl ketone.

The second lubricious coating is less lubricious than the firstlubricious coating (i.e., it is less lubricious than a coating having100% of the first amount of lubricious material), and is preferably lesslubricious than a coating having as little as about 5% to about 10% ofthe first amount of lubricious material). Thus, the second lubriciouscoating has a slip angle which is greater than a slip angle of alubricious coating having an amount of lubricious material which isabout 5% to about 100% of the first amount. Surprisingly, a lubriciouscoating having about 5% to about 10% of the first amount of lubriciousmaterial had a slip angle about equal to the slip angle of the firstlubricious coating, and thus was not significantly less lubricious thanthe first lubricious coating. For example, a 3.0 mm outer diameterballoon coated with a lubricious coating having about 5% of the firstamount of lubricious material (i.e., coated with a solution of about 5wt % of the first lubricious coating 40 solution) had a slip angle ofabout 6 to about 9 degrees, compared to a slip angle of about 4 to about7 degrees for a similar 3.0 mm outer diameter balloon coated with thefirst lubricious coating 40.

While illustrated on the entire outer surface of the balloon 24, thesecond lubricious coating 41 may alternatively be on less than theentire outer surface of the balloon. Similarly, none or only part of theexposed outer surface of the tip 27 may be coated with the secondlubricious coating 41, and may alternatively be coated in whole or inpart with the first lubricious coating 40 or a different coating. InFIG. 1, the first lubricious coating 40 is on the entire exposed outersurface of the outer tubular member 14 (i.e., from the end of theadapter/strain relief member at the proximal end of the catheter, to theproximal shaft section 25 of the balloon 24). However, the firstlubricious coating 40 may be on only part of the exposed outer surfaceof the outer tubular member, and is preferably on at least a distalsection of the exposed outer surface of the outer tubular member (e.g.,a distal section equal to about 18 to about 22% of the length of theouter tubular member 14). In a presently preferred embodiment, theproximal end of the coating 40 on the shaft is located distal to theproximal adapter 28. In the embodiment in which the balloon catheter isa rapid exchange type catheter having a guidewire proximal port locateddistal to the proximal end of the catheter, the first lubricious coatingpreferably extends along at least the exposed outer surface of the shaftdistal to the guidewire proximal port, although it may alternativelyalso extend along the exposed outer surface of the tubular memberforming the proximal shaft section proximal to the guidewire proximalport.

Although the coatings 40, 41 are illustrated with aligned ends at theproximal end of the balloon in the embodiment of FIG. 1 (i.e., thedistal end of the coating 40 is at the proximal end of the coating 41),so that the coatings may abut one another, it should be understood thatthe coatings may alternatively overlap one another. For example, thefirst coating 40 may extend in part onto an outer surface of theballoon, or the second coating 41 may extend in part onto an outersurface of the outer tubular member, due to the manufacturing tolerancesof the coating procedure. Thus, in one embodiment (not shown) a distalportion of the first coating 40 extends along at least a proximalsection of the balloon and is subsequently covered by a proximal portionof the second coating 41, so that the proximal portion of the secondcoating 41 overlaps the distal portion of the first coating 40. However,in a presently preferred embodiment, the interface between the exposedouter surface ofthe first coating 40 and the exposed outer surface ofthe second coating 41 is located at (i.e., radially aligned with) theproximal end of the balloon, irrespective of whether the coatings are inan abutting or overlapping relation. Alternatively, the interfacebetween the exposed outer surface of the first coating 40 and theexposed outer surface of the second coating 41 may be proximal or distalto the proximal end of the balloon.

In a method of dilating the stenosed section 31, the balloon catheter 10is advanced within the blood vessel 30 to position the balloon 24 at adesired position at the stenosed section 31. The balloon 24 is inflatedso that the balloon working length contacts and dilates the stenosedsection 31 of the blood vessel 30. FIG. 4 illustrates the inflatedballoon in contact with and dilating the stenosed section 31. Theinflated balloon in contact with the blood vessel/lesion preferably doesnot longitudinally slip, or at least has an insubstantial amount ofslippage proximally or distally from the desired position at thestenosed section 31 during the dilatation. After the balloon is inflatedone or more times to dilate the stenosed section 31 as is conventionallyknown, and the balloon is deflated a final time, to allow forrepositioning or withdrawing the balloon catheter from the blood vessel.The lubricious coatings 40 and 41 remain on the catheter outer surfaceto facilitate removal or repositioning of the balloon catheter in theblood vessel.

To the extent not previously discussed herein, the various cathetercomponents may be formed and joined by conventional materials andmethods. For example, the outer and inner tubular members 14, 16 can beformed by conventional techniques, such as by extruding and neckingmaterials found useful in intravascular catheters such apolyethylene,polyvinyl chloride, polyesters, polyamides, polyimides, polyurethanes,and composite materials. The length of the balloon catheter 10 isgenerally about 108 to about 200 centimeters, preferably about 137 toabout 145 centimeters, and typically about 140 centimeters for PTCA. Theouter tubular member 14 has an outer diameter (OD) of about 0.017 toabout 0.036 inch (0.43-0.91 mm), and an inner diameter (ID) of about0.012 to about 0.035 inch (0.30-0.89 mm). The inner tubular member 14has an OD of about 0.017 to about 0.026 inch (0.43-0.66 mm), and an IDof about 0.015 to about 0.018 inch (0.38-0.46 mm) depending on thediameter of the guidewire to be used with the catheter. The balloon 24is has a length of about 14 mm to about 46 mm, typically about 8 mm toabout 40 mm, an inflated working diameter of about 1.5 mm to about 5.0mm.

While the present invention has been described herein in terms ofcertain preferred embodiments, those skilled in the art will recognizethat modifications and improvements may be made without departing formthe scope of the invention. For example, although the embodimentillustrated in FIG. 1 has an outer and inner tubular member defining theinflation and guidewire lumens, respectively, the shaft mayalternatively comprise a dual-lumen design as is conventionally known.Moreover, while individual features of one embodiment of the inventionmay be discussed or shown in the drawings of the one embodiment and notin other embodiments, it should be apparent that individual features ofone embodiment may be combined with one or more features of anotherembodiment or features from a plurality of embodiments.

1. A method of making a balloon catheter, comprising: a) providing ashaft of a balloon catheter with a first lubricious coating by applyinga first solution having a first concentration of a lubricious materialon at least a portion of the shaft; b) providing a balloon of theballoon catheter with a second lubricious coating by applying a secondsolution having a second concentration of the lubricious material on atleast a portion of the balloon, the second concentration being not morethan about 2.5% of the first amount; and c) curing the solutions, toform a balloon catheter having a lubriciously coated balloon having ahigher slip angle than the lubriciously coated shaft.
 2. The method ofclaim 1 wherein the concentration of the first solution is about 1.0 toabout 1.3 wt. % lubricious material and the concentration of the secondsolution is about 0.01 to about 0.03 wt. % lubricious material, and thesolutions are applied by a method selected from the group consisting ofwiping, spraying, and dipping.
 3. The method of claim 1 includingapplying the second solution to an entire length of an outer surface ofthe balloon and to at least a portion of an outer surface of a distaltip section of the shaft distal to the balloon.